Iron-glass seal having nickel-iron contact prongs



April 22, 1941. A. w. HULL 2,239,423

IRON-GLASS SEAL HAVING NICKEL-IRON CONTACT PRONGS Filed April 7, 1959Inventor: Albert W. Hui I,

His Attorney.

Patented Apr. 22, 1941 IRON-GLASS SEAL HAVING NICKEL-IRON CONTACT PRONGSAlbert W. Hull, Schenectady, N. Y., asslgnor to General ElectricCompany, a corporation of New York Application April 1, 1939, Serial No.266,603

3 Claims.

The present invention relates to improvements in lead-in arrangements,and while not limited thereto, is especially applicable in connectionwith metal enclosed vacuum tubes.

In the manufacture f metal radio tubes and the like, considerations ofeconomy make it desirable that the envelope structure be constituted inso far as possible of iron or, more specifically, of a commercial gradeof steel. However, where the entire wall structure of the tube consistsof iron, difliculty is encountered in the formation of satisfactoryseals for the lead-in conductors. For example, where glass is used asthe sealingin material it is an important requirement that the glassemployed be matched to the expansion characteristics of the envelopematerial and that the lead-in conductors themselves be equally wellmatched to the glass.

This requirement can be met in one way by making both the conductors andthe header of iron and utilizing an iron-matching glass such asdescribed in A. W. Hull and Louis Navias application Serial No. 266,604,filed April 7, 1939. However, where, as above specified, it is desiredto have the external portions of the conductors serve as contact prongsfor engagement with a tube socket, the use of iron occasions somedifilculty. In particular, it is found that .the tendency of the iron tooxidize makes the establishment of a good contact with the socketuncertain. I

In accordance with my present invention this dlfliculty is overcome byforming the header of a commercial grade of iron or steel and the leadinconductors of an alloy comprising from '70 to 80 per cent-nickel withremainder iron. Such alloys are highly resistant to oxidation so thatcontact surfaces which embody them tend to remain clean for normalconditions of use. On the other hand, their expansion characteristicssubstantially match those of iron so that a glass which seals to onewill also seal to the other.

The features which I desire to protect herein are pointed out withparticularity in the appended claims. The invention itself, togetherwith further objects and advantages thereof, may best be understood byreference to the following description taken in connection with thedrawing in which Fig. 1 shows a vacuum tube suitably embodying theinvention; Fig. 2 is a bottom plan view of the tube of Fig. 1; and Fig.3 is an enlarged fragmentary detail of one of the lead-in seals used inthe tube.

Referring particularly to Fig. 1, there is shown a metal vacuum tubecomprising an elongated metal cylinder l which is closed at both ends.

The envelope encloses appropriate electrode structure of which only thelead conductors H are illustrated. The lower end of the envelope isclosed by means of a circular headerl3 which is peripherally joined tothe cylinder ID, for example, by soldering, and through which the leadinconductors i2 project. The header is provided centrally with aprojecting tubulation I l which serves as a guide pin for assisting thelocation of the tube in an appropriate socket. 'The plan view given inFig. 2 shows the relative arrangement of the tubulation i4 and thelead-in conductors l2.

For making connections between the internal electrode structure andsuitable external circuits, use is made of the outwardly extendingportions of the lead-in conductors l2. To this end they are shaped andotherwise adapted to be used as contact prongs for engagement withcooperating socket terminals. In particular they are made of suflicientstiffness so that they will not bend unduly when subjected to thepressure necessary to engage them with a socket of the usual type.

In the arrangement of Fig. l, the contact pins or prongs are illustratedas passing through insulating socket plates 45 and it which are adaptedto support appropriate terminals. One such terminal is shown at i8 ascomprising a metallic part shaped to engage its associated contact pinin good electrical contact.

In order to retain the lead-in conductors i2 in insulatingly spacedrelation to the header i3, use is made f seals of the'general typedescribed and claimed in the copending application of H. L. Thorson,Serial No. 266,569, filed April '7, 1939. As is shown more clearly inFig. 3, the structure of each seal includes a shallow depression formedin the header by means of deformation of the metal thereof. The shape ofthe depression is such that it includes a peripheral wall portion iswhich extends transversely to the principal plane of the header and aflattened floor portion 20 which is parallel to the plane of the header.The lead-in conductor i2 is sealed in a body of fusible vitreousmaterial 22 and by means of this material is supported within an opening2| formed centrally in the floor portion 20. The fusible materialincludes a portion which substantially fills the depression formed inthe header i3 and a further portion in the form of a rounded moundadhering to the header on the side opposite the depression.

In the application contemplated in the present instance both theenvelope cylinder l0 and the header H are constituted of iron. (By theterm iron I mean to designate low carbon steels generally such, forexample, as cold rolled steel or deep drawing steel.) In order thatvacuum-tight seals may be made under these conditions it is necessarythat the vitreous material 22 comprise a substance which substantiallymatches the expansion characteristics of iron. As is explained in theHull and Navias application Serial No. 266,604 previously referred to,this requirement is fulfilled by the use of a glass whose theoreticaloxide composition falls approximately within the following limits; Bio:and 3:0: in the sum of from 40 to 50 per cent, the B20: being present inthe amount of less than 5%; K20 and NazO in the sum of 16 to 20 percent; PhD and BaO in the sum of from 28 to 35 per cent, the PhD beingpresent in the amount of at least per cent, and CaO and Cal: in the sumof from 3 to 6 per cent. A preferred glass within the foregoingclassification comprises about 45% S102, about 12% mo; about 6% NazO,about 32% PbO and about 5% CaFz. This glass has expansioncharacteristics which enable it to be sealed readily to iron and it isfurthermore characterized by high resistance to heat shock and tochemical attack.

It is apparent that if the lead-in conductors I! are also constituted ofiron, they may be expected to seal to a glass of the character describedabove as satisfactorily as does the header itself. However, for presentpurposes, where it is desired to have the externally projecting portionsof the lead-in conductors serve also as contact pins, it is desirablethat they be constituted of a material less readily oxidizable thaniron. In accordance with my present invention this result may beobtained without impairing the perfection of the seal by utilizing forthe lead-in conductors an alloy containing from 70 to 80 per -centnickel with remainder iron. Alloys of this classification are highlyresistant to oxidization or other chemical attack, but are neverthelesswell adapted to sealing with the glasses which seal to iron: Aparticular alloy with which I have obtained especially satisfactoryresults is that comprising 78% nickel and 22% iron.

While I have described my invention in connection with a particular sealarrangement it will be understood that it is by no means limited to usewith such an arrangement. I, therefore, aim in the appended claims tocover all such alternative .uses as, come within the true spirit of alow carbon steel and having an opening therein, the said opening beingsealed by a body of aglass which has substantially the expansioncharacteristics of said steel throughout the range of temperaturesnormally encountered in the operation of the device and which is fuseddirectly to the said iron wall portion, and a lead-in conductorextending into the said enclosure through the said body of glass and insealing relation with the glass, the said conductor being constituted ofan alloy of from '70 to 80 per cent nickel with remainder iron and theexternally projecting portion of the conductor being shaped to serve asa contact prong.

2. An electrical discharge device comprising electrode structure, anelongated cylindrical envelope enclosing the electrode structure, acircular header constituted wholly of low carbon steel closing one endof the envelope and having a plurality of openings therein, the openingsbeing respectively sealed by bodies of a glass which has substantiallythe expansion characteristics of the header material throughout therange of temperatures normally encountered in the operation of thedevice and which is fused directly to the header, and rigid lead-inconductors for the electrode structure respectively sealed through thevarious bodiesof glass, the said conductors being constituted of analloy of from to per cent nickel with remainder iron, whereby theexpansion characterstics of the conductors are matched to those of thesaid glass and the header material and the externally projectingportions of the conductors are suillciently non-oxidizable to servesatisfactorily as contact prongsfor engagement with socket terminals.

3. A vacuum tube comprising electrode structure, an elongatedcylindrical metal envelope surrounding the electrode structure, acircular header of low carbon steel closing one end of the envelope andprovided with a plurality of openings therein, the openings beingrespectively closed by bodies of a glass which has substantially theexpansion characteristics of the header material throughout the range oftemperatures normally encountered'in the operation of the device andwhich .is sealed directly to the header, and rigid lead-in conductorsfor the electrode structure sealed through the various bodies of glass,the said conductors being constituted of an alloy of approximately '78per cent nickel and 22 per cent iron, whereby the expansioncharacteristics of the conductors match those of the glass and headermaterial and the externaily projecting portions of the conductors aresufliciently non-oxidizable to serve satisfactorily as contact prongs.

- ALBERT W. HULL.

